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Compare final print resolution, different formats

Recently I made an extensive spreadsheet that compared the different formats,

Categorized by format diagonal

35mm - 13 MP
35mm - 17MP

MF Dig - 16MP
MF Dig - 22MP
MF Dig - 39MP

MF 6x7 Film

LF 4x5 Film

LF 8x10 Film

The graph below shows the max. final print resolution for 8" print (you can interpolate upwards) with many variables taken in consideration. I set up 5 scenes of varying DOF, ranging from the far left block of 35mm shooting at f2.8, the next scene 35mm required f4, the next scene 35mm required f5.6.... and finaly f8. Each format, according to film/sensor diag. had a proportional increase in f stop vs. the 35mm, which was the starting point since it's the smallest format. The f stop increase is indicated in the legend. For example, the second block from the right shows f stops at....

All these f stops produce the same DOF, as the lens fl increases for each format.

The final block to the right, which is an infinity scene, whereas each format was shot at its optimum f stop.

It is interesting to see just how superior 45 and 810 is when shot at infinity. (or a flat wall) It is equally interesting to see how MF 6x7 rivals 4x5 in extreme DOF scenes. (Which puts LF lenses and RFB in no-mans-land) Here is some notes regarding the graph....

1. All formats reduced to digital file, so scanner efficiency taken into consideration for film.

2. MF, 6x7 was based on high end MF cameras / lenses. I used Mamiya M7 tested results. This is quite different then using RFB using LF lenses / view cameras.

3. Digital values used based on testing and makers specification sheets.

4. This graph represents color images only, not B&W, in which case, B&W film would excel over digital to a greater extent.

Compare final print resolution, different formats

That is really interesting to see, but I am confused. You tested some formats, and others you used manufacturer's theoretical specs? The 16 and 22 mp backs seem to have identical responses, that is surprizing.

Compare final print resolution, different formats

Photodo did a similar experiement ... http://www.pbase.com/image/50899836

they found the choice of film made a decisive difference. 35mm tmax actually appeared sharper and higher resolution than 4x5 tri-x. They show theoretical (MTF) and empirical (their own test target pictures) results. No real world subjects, though.

Possibly some discrepancy with optical quality. They use one of the highest quality modern zeiss lenses on the 35, and am old sironar on the 4x5.

Compare final print resolution, different formats

Craig, as for data..... where actual test results were available they were used. Where they were not available, if it made more sense to interplolate from smaller formats or other similar tests, then I did such. In some cases, such as 39MP sensors, which have not hit the market yet, I had to interpolate using data from similar sensors and upsizing it accordingly.

As for the 16MP and 22MP having the same results....this is true... here is why, the analysis was only done on the short side of the recording media / print. In the case of the 16MP and 22MP, the two sensors were of different formats....

16 mp = 4080 x 4080
22 mp = 4080 x 5436

Since the pixel density was equal on the short side, the results were the same. But the 22MP would make a slightly larger horizontal print. I used the short side, to simplify the comparisons.... of course, the 35mm is 1.5 aspect ratio, vs. all the remaining formats 1.25 aspect ratio. (other than the 16MP square format) For all intensive purposes, you can just eliminate the 16MP results as it was the only square format, and the 22MP is of similar pixel density and is 1.33 format, close enough to 1.25 for this simple representation.

From these "short side" results, you can interpolate as you please with theoretical crops and get additional data that meets someones specific needs. For example, if someone wants to compare everything to the 35mm, 1.5 aspect ratio, then you need to reduce the height
(short side) of the 1.25 aspect ratio formats by,

4x5 = 5/4 = 1.25

reduce short side to 5/1.5 = 3.33, or a .666" reuduction, or in %'s

.666/4 = 16%

So if you reduce all the 1.25 aspect ratios results by 16%, you will have everything on even par with 35mm's aspect ratio of 1.5. Of course, others may want to crop 35mm to meet the 1.25 aspect ratio. There is endless possibilities to these types of format comparison, hence why I just picked the short side to get a feel for the relationships between formats.... play with the results as you please to fit the aspect ratio you desrie.

Hope this does not side track the intent of the graph....it's purpose is to show just how much difference there is in final print resolution based on the amount of DOF in a scene. The results surprised me a bit, on both ends! At infinity, LF simply rules...but extreme DOF scenes (of course front tilt is not being considered, as its used in a small % of scenes), I was shocked to see just how competitive a good MF system is. When considering the size, weight issues, in many cases, its a tough format to beat. Of course the Mamiya 7 system which I based this from, is an exceptionaly sharp camera system, due to the best optics combined with near perfect film flatness. But has limitations in lens available, no movements, etc. But I also put LF in its best light, considering the most modern LF optics and drum scans, all based on personal testing.

In the end, DOF is the dagger to LF as it forces the use of higher f stops, which introduces diffraction to the 1/R camera systems total resolution, which includes both the point-of-exact-focus and all the way out to the defocus of the near/far. As you can see, in a large DOF scene (second block from the right), 8x10 is severely injured by diffraction, yet 4x5 is just on the edge of being severely effected, hence why 8x10 will only produce an overall 20% improvement in sharpness vs. 4x5. Surely not worth all the expense, size, weight, of 8x10 vs. 4x5. But at infinity, well, 810 earns its wings, and produces the expected 100% increase in resolution.

So for newcomers, who are trying to select camera gear to best meet their needs, I think this information is very helpful, something I wish I better understood in my early days. Bottom line, unless you shoot at infinity, (or shoot flat subjects), 4x5 is truly a remarkable format in this era. It seems to fall in diffractions "grey area", as it relates to modern optics and modern films of today. Of course, this was NOT the case 50+ years ago, when optics and films resolution were so inferior. This explains in yesteryears, why even larger formats (ULF) were so common, they produced better results. This also explains why I have seen 16x20 contact prints, that simply don't impress me, as the higher f stop counteracts the larger film size. I have come accross a few ULF shooters, that don't fully grasp this. Of course some do, they just prefer using a huge camera. But I beleive the majority of LF photographers are mainly after image quality in the final print, and to those, this graph may be of help, as many of us have budgets, travel issues, physical limitations to weight of gear, etc.

As for 5x7, the results would have fallen relatively proportional between 4x5 and 810.

Compare final print resolution, different formats

Dan, the metrics are so very elementary and obvious that from day-one I never needed to elaborate upon them in order to justify a larger and sometimes smaller format. Topics mired in optical bench racing are usually begun with an abstract, generally poorly qualified case and go on forever with silly minutiae. Further, as it concerns this kind of case, I have not read an original, truly contributory addition to the knowledge base for many years; it's all just someone reinventing data, often with irrelevance and in error.

Compare final print resolution, different formats

The practical questions might be along the lines of "If I use really fine grained film in a smaller format could I match or exceed the quality of faster film in a larger format?" Given that you might be able to shoot with a larger aperture and slow film in a smaller format versus needing to stop down and shoot with faster film with a big camera.

The real world answer depends on many more factors than the ultimate test results. If you want to capture still leaves on a windy day, or shoot a fleeting moment - those are the questions that most often determine camera choice, even when you are willing to work as hard as possible to get the "ultimate" quality.

Compare final print resolution, different formats

John, I sort of agree with you for work at normal distances, but for work at magnifications above 1:1 it does pay to calculate the limits before wasting much film. One doesn't have to do it very well or more than once, and I agree with you that the results aren't worth publishing. Dut I think everyone who wants to work much above 1:1 should do the exercise once. The news from it is mainly bad; since we're most of us optimists, finding the bad news ourselves is good for us.

Compare the cavalierly-expressed rules of thumb about optimal aperture given magnification in Brian Bracegirdle's book Scientific Photomacrography with the deeper and mind-numbing treatment of the problem in H. Lou Gibson's Photomacrography. Both authors are highly-experienced, know very well what they're doing, and are very thoughtful. Bracegirdle's advice is easier to apply, Gibson's seems to work a little better.

Compare final print resolution, different formats

Tests like this also presume that test chart resolution equates with subjective quality of a print ... a premise that's been dismissed by most of the research.

I think the results are interesting, but ultimately not very useful. The photodo test take film into account, and in doing so give you more to work with. They also spell out how quality in the smaller formats is much more closely tied to film performance than in the larger ones. This is practical and helpful.